I wrote the original version of this in total isolation with no access to the internet or any research materials other than a basic reference manual for JavaScript. I had to reverse engineer a system for building puzzles according to a specified difficulty level, so not only did I have to solve how Sudoku is made, I also had to figure out how to program it. I am very proud to say my work was 100% original with no outside influence.
Built v0 on paper, you can see the photos below
I was unable to keep a digital copy of the original code, so I hand recorded it as best I could onto notebook paper. This code is no longer functioning properly and I may never walk back through it, it did in it's original form function as expected.
Attempting to keep as much of the original form, I did not want to dramatically change the architecture of the original program. Primarily, I have cleaned up the code and implemented a more modern standard using HTML5(Flexbox), ES6, as well as clean up of comments, naming conventions, implementation of file separations utilizing imports/exports.
Future overhaul to take place at some as yet unknown date.